Most canker sores heal on their own within 4 to 14 days, but you can shorten the pain and speed recovery with the right combination of rinses, topical treatments, and habit changes. Minor canker sores, the kind most people get, are typically 2 to 5 mm across. Larger ones (1 to 3 cm) can linger for up to six weeks. Here’s what actually works to get rid of them faster.
Rinse With Salt Water or Baking Soda
A simple alkaline rinse is one of the most effective first steps. It reduces acid in your mouth, keeps the sore clean, and creates an environment that promotes healing. St. Jude Children’s Research Hospital recommends this formula: 4 cups of warm water, 1 teaspoon of table salt, and 1 teaspoon of baking soda. Swish gently for 30 seconds and spit. Repeat three to four times a day, especially after meals.
The rinse works because food particles and mouth bacteria slow healing when they sit on the open sore. Salt draws out fluid to reduce swelling, while baking soda neutralizes acids that irritate the ulcer. It won’t taste great, but you’ll often notice less pain within a day of starting.
Use an OTC Numbing Gel
Benzocaine-based gels like Orajel and Anbesol temporarily numb the sore so you can eat and talk without wincing. Apply a small amount directly to the ulcer with a clean finger or cotton swab. The numbing effect varies by product. In a comparison of three popular canker sore medications, all produced meaningful pain relief, though duration and intensity differed between brands. Reapply as directed on the label, usually every few hours.
Protective pastes that form a barrier over the sore are another option. Products containing a bioadhesive base stick to the wet tissue inside your mouth and shield the ulcer from food, drinks, and friction. This physical barrier can be more helpful than numbing alone if your sore is in a spot that constantly rubs against your teeth or cheek.
Avoid Irritating Foods and Products
What you stop doing matters as much as what you start doing. Acidic foods like citrus, tomatoes, and vinegar-based dressings sting on contact and can delay healing. Spicy foods, crunchy chips, and crusty bread physically scrape the ulcer. Stick to softer, blander foods until the sore closes.
Your toothpaste may also be making things worse. A systematic review of clinical trials found that toothpastes containing sodium lauryl sulfate (SLS), a common foaming agent, significantly increased canker sore frequency, duration, and pain compared to SLS-free alternatives. Switching to an SLS-free toothpaste reduced all four measures across the studies reviewed. If you get canker sores more than a couple of times a year, checking your toothpaste ingredient list is one of the simplest changes you can make. Brands like Sensodyne, Biotene, and some Arm & Hammer varieties skip SLS entirely.
Check for Nutritional Gaps
Recurrent canker sores are linked to specific vitamin and mineral deficiencies, particularly vitamin B12, folate, and iron. One study found that people with recurring canker sores had significantly lower daily intake of both B12 and folate compared to people who rarely got them. Roughly 14 to 18 percent of patients with recurrent sores show measurable nutritional deficiencies on blood tests, and replacing those missing nutrients often improves symptoms.
You don’t necessarily need a blood test to act on this. If your diet is low in leafy greens, legumes, eggs, meat, or fortified cereals, those are the main dietary sources of B12 and folate. A basic B-complex supplement or a daily multivitamin with iron and zinc is a reasonable step if canker sores keep coming back. For persistent deficiencies, your doctor can check levels with a simple blood draw.
When a Canker Sore Needs Medical Treatment
Most canker sores don’t need a doctor. But Cleveland Clinic recommends scheduling an appointment if a sore lasts longer than two weeks, is larger than a centimeter (roughly the size of a pea), comes with flu-like symptoms, returns two or three times a year, or interferes with eating and drinking.
For severe or stubborn sores, a doctor can prescribe a steroid dental paste. These pastes, applied after meals and at bedtime, form a thin film over the ulcer that reduces inflammation and speeds healing. You press a small amount onto the sore with a cotton swab rather than rubbing it in, since the paste becomes gritty if disturbed. Prescription-strength treatment is typically reserved for major-type ulcers, the deep, large ones that can take six weeks to resolve on their own.
Putting It All Together
For the fastest relief, layer your approach. Start rinsing with the salt and baking soda solution several times a day. Apply a numbing or protective gel before meals. Cut out acidic and sharp-edged foods. And switch to an SLS-free toothpaste to reduce your odds of the next one. Most minor canker sores will be noticeably better within a week using this combination, with full healing by day 10 to 14. If you’re someone who gets them repeatedly, addressing B12, folate, and iron intake can make a real difference in how often they show up.